Hi, There is an example of +RTS -s output at the end. I have few simple questions: What does "9 Mb total memory in use" mean? Is it in mega bytes (MB) or in mega bits (Mb)? I would expect memory usage to be in bytes (B) but a unit for bits (b) seems to be used. Looks like heap size in mega bytes... What does MUT abbreviation stand for? Peter. 1,175,063,464 bytes allocated in the heap 25,951,288 bytes copied during GC (scavenged) 929,036 bytes copied during GC (not scavenged) 3,932,160 bytes maximum residency (4 sample(s)) 2237 collections in generation 0 ( 0.15s) 4 collections in generation 1 ( 0.04s) 9 Mb total memory in use INIT time 0.00s ( 0.00s elapsed) MUT time 2.95s ( 20.33s elapsed) GC time 0.19s ( 0.20s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 3.15s ( 20.53s elapsed) %GC time 6.0% (1.0% elapsed) Alloc rate 397,455,026 bytes per MUT second Productivity 93.9% of total user, 14.4% of total elapsed